Nematodes are unsegmented helminths with bilateral symmetry, have a fully functional digestive tract, are usually long and cylindrical, and vary from a few millimeters to over a meter long. The number of people infected with Ascaris lumbricoides worldwide is probably second only to the number infected with the pinworm, Enterobius vermicularis. Eosinophilic gastroenteritis is an inflammatory disease characterized by eosinophilic infiltration of the gastrointestinal tract accompanied by varying abdominal symptoms and usually by peripheral eosinophilia. The T-cell component of the immune system plays an important role in resistance to gastrointestinal nematodes. E. vermicularis is thought to cause the world’s most common human parasitic infection. Infection with Trichuris trichiura is more common in warm, moist areas of the world and is often seen in conjunction with Ascaris infections. Worm burdens vary considerably, and individuals with few worms are unaffected by the presence of these parasites. C-reactive protein, α-antitrypsin, total globulin, and fibronectin levels and plasma viscosity were significantly higher in children with T. trichiura dysentery. Hookworm infections are found in moist, warm areas and are responsible for much human disease, although they cause more morbidity than actual mortality. Infection in humans is acquired through active skin penetration of filariform larvae from the soil. Trichostrongylus spp. are small worms, similar to hookworms, and live embedded in the mucosa of the small intestine. The definitive diagnosis of Trichostrongylus spp can be made by identification of eggs in the stool. Finally, the chapter talks about Strongyloides spp.

Ascaris lumbricoides. Two spot films from an upper gastrointestinal barium study show that white barium in the small bowel outlines an adult worm that has displaced the barium and appears dark. (From a Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)

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Figure 10.6

Ascaris lumbricoides. Two spot films from an upper gastrointestinal barium study show that white barium in the small bowel outlines an adult worm that has displaced the barium and appears dark. (From a Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)

Ascaris lumbricoides. Small bowel barium study shows adult worms that present as longitudinal dark lines against the white barium in the small bowel. The worms have ingested the barium, and their guts appear as white lines between the dark body outlines. (From a Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)

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Figure 10.7

Ascaris lumbricoides. Small bowel barium study shows adult worms that present as longitudinal dark lines against the white barium in the small bowel. The worms have ingested the barium, and their guts appear as white lines between the dark body outlines. (From a Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)

Numerous adult Trichuris trichiura worms attached to the colonic mucosa of a patient who died of trichuriasis. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)

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Figure 10.18

Numerous adult Trichuris trichiura worms attached to the colonic mucosa of a patient who died of trichuriasis. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)

(Upper) Strongyloides stercoralis rhabditiform larva; note the packet of genital primordial cells toward the right side of the image. (Lower) S. stercoralis rhabditiform larva; note the packet of genital primordial cells in the middle of the field (enlarged).

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Figure 10.29

(Upper) Strongyloides stercoralis rhabditiform larva; note the packet of genital primordial cells toward the right side of the image. (Lower) S. stercoralis rhabditiform larva; note the packet of genital primordial cells in the middle of the field (enlarged).

4. Ashford,R. W.,, and G.Barnish.1990.Strongyloides fuelleborni and similar parasites in animals and man, p. 271–286.InI.E. Grove (ed.), Strongyloidiasis: a Major Roundworm Infection of Man.Taylor and Francis,London, United Kingdom.